Rotary fasteners for ski boots are already known in various constructions. One of these known rotary fasteners is disclosed for example in German Patent Specification No. C-22 13 720. In this case a rotary knob which actuates a rotary fastener is connected so as to be fixed against relative rotation directly to a driving disc which acts as a drive reel and has eccentrically arranged drive journals which come into engagement successively with radial guide grooves provided as drive elements on the upper face of the wire reel during the rotary movement of the rotary knob. This produces a sort of Maltese cross transmission for the rotary drive of the wire reel. In this way the closure flaps of an appertaining sports shoe can be tightened or loosened in stages. The rotary fastener according to U.S. Pat. No. 3,738,027 is constructed according to approximately the same basic principle.
A further embodiment of a rotary fastener is known from European Patent Specification No. B-56 953. In this device a pawl forming part of a ratchet arrangement is associated with an appropriate recess in the lower half of a housing body to be fixed on the upper of the shoe, whilst the pawl which is constructed with an engaging tooth and a projecting shoulder and is prestressed upwards is mounted so as to be pivotally movable in a recess in the cover-like upper half of the said stationary housing body. A toothed ring which is provided with engaging teeth is arranged inside a rotary knob of approximately cup-like construction arranged above the said housing body so that the teeth of the toothed ring can come into engagement with the pawl. The toothed ring has an upwardly protruding projection which has an external multiple coarse thread which engages with a corresponding internal thread in the centre of the rotary knob in such a way that when the rotary knob is to be turned in one direction with a view to closure it first carries out an axial free movement on the coarse thread until it has brought the toothed ring into engagement with the pawl and then entrains the toothed ring during a further rotary movement, producing a sort of ratchet effect through the co-operation of the toothed ring and the pawl. If the rotary fastener is then to be opened again, the rotary knob is turned in the opposite direction and again first of all carries out a free rotation on the coarse thread of the toothed ring until the toothed ring is disengaged from the pawl, whereupon the actual loosening is effected during the further rotation of the rotary knob.
If only the coarse thread engagement between the toothed ring and the rotary knob used to produce the free rotation in this known construction according to European Patent Specification No. B-56 953, is considered this not only gives a particularly expensive construction, and resulting high manufacturing costs, but also it necessitates an undesirably overall height, on the one hand because of the design and construction, and on the other hand because of the possible axial movement of the rotary knob.